(1) Field of the Invention
The invention relates to the field of radiocommunications networks, whether by satellite or terrestrial, and it relates more particularly to routing traffic between communications terminals attached to such networks.
(2) Description of Related Art
The term “radiocommunications network, whether by satellite or terrestrial” is used therein to mean a communications network such as a mobile telephone network of the GMS/GPRS (global system for mobile communications, general packet radio system) or of the UMTS (universal mobile telephone system) type, in which traffic exchanged by communications terminals needs to transit via a call switching center (known as a mobile services switching center (MSC)) for handling calls set up in a given geographical area, with transit between said area and the MSC taking place via a portion of a transmission network in the form of a terrestrial link or a communications satellite link coupled to two transmission equipments, each connected to a traffic router. The two traffic routers and the two transmission equipments may be installed either at the so-called “A-bis” interface level of the network, i.e. between certain base stations and the associated base station controller, or else at the so-called “A-ter” interface level, i.e. between a base station controller and a transcoder coupled to the associated MSC and serving to convert compressed voice into digitized speech at 64 kilobits per second (kbps) or even at the so-called “A” interface level, i.e. between said transcoder and said MSC.
By way of example, in satellite transmission networks, and as is known to the person skilled in the art, using a remote link via a satellite constitutes a solution that is particularly attractive for operators when they desire to deploy networks rapidly over sites that are very widespread geographically speaking and/or dispersed over large territories, without that requiring terrestrial infrastructure that is cumbersome and expensive.
Unfortunately, the cost of operating a satellite retransmission network, in the present state of the art, is almost insurmountable given the cost of renting satellite resources.
In an attempt to remedy that drawback, at least two solutions have been proposed. A first solution consists in using MSCs that are relocated downstream from the transmission equipments, which amount to installing an MSC in each remote site. However that solution is very expensive, in particular because it requires complex protocol layers to be processed on a large number of channels, and it turns out to be prohibitive outside situations in which distant sites, to which MSCs have been relocated, cover a very large number of network subscribers, typically at least 400,000.
A second solution consists in constituting specific local configurations integrating all of the elements of the network but for reduced capacity. However that solution requires specific development that is very expensive and therefore not profitable. In addition, that solution turns out to be incompatible with existing networks because they generally make use of proprietary solutions that require complex integration processes.